1. Field of the Invention
The present invention relates to a driving technique for driving a motor.
2. Description of the Related Art
Electronic devices having an image acquisition function such as digital still cameras, digital video cameras, camera-mounting cellular phones, etc., have a camera shake correction function. FIGS. 1A and 1B are diagrams showing a configuration of an image acquisition apparatus having a camera shake correction mechanism. Referring to FIG. 1A, an image acquisition apparatus 200 includes an image acquisition sensor 202, a lens 204, a lens holder 206, an actuator (motor) 208, a gyro sensor 214, a Hall effect element 216, and a motor control circuit 218.
The lens 204, which is used to perform camera shake correction, is positioned on an optical axis 220. The lens holder 206, which is used to hold the lens 204, is supported by a shaft 209, which allows the lens holder 206 to be moved in the X-axis direction. FIG. 1B is a perspective view showing a camera shake correction mechanism. The same movable mechanism as that used for the X-axis direction shown in FIG. 1A is also provided for the Y-axis direction. Thus, such an arrangement allows the lens holder 206 to be moved along the XY plane. In order to prevent focusing error due to displacement of the lens in the Z-axis direction, the lens holder 206 is fixed in the Z-axis direction.
The actuator 208 has a configuration including a magnet 210 which is the mover and a pair of coils 212 which is the stator. The mover 210 is provided on the lens holder 206 side, and the coils 212 are provided on a printed-circuit board. Conversely, in some cases, the coils 212 are provided on the lens holder 206 side, and the magnet 210 is provided on the printed-circuit board.
The Hall effect element 216 receives the magnetic field generated by the magnet 210, and generates a Hall signal which indicates the position of the magnet 210, i.e., the position of the mover. The gyro sensor 214 detects vibration of the image acquisition apparatus 200, and generates a gyro signal which indicates the amount of displacement. The control circuit 218 receives the gyro signal and the Hall signal. The control circuit 218 generates a driving signal to be supplied to the coil 212 by performing a feedback operation such that the displacement of the image acquisition apparatus 200 indicated by the gyro signal and the displacement of the lens 204 driven by the actuator 208 cancel each other out. FIG. 1 shows a camera shake correction mechanism configured to correct camera shake in the X-axis direction. Also, the same mechanism is provided for the Y-axis direction. An arrangement may be made in which the image acquisition sensor is moved instead of the lens in order to correct camera shake. In such an arrangement, a camera shake correction mechanism is provided in the same way.